The present invention relates to the in situ monitoring and control of the thickness of a thin film during deposition on a wafer.
In conventional processes, polycrystalline silicon is deposited on oxidized silicon by chemical vapor deposition. It is important to accurately monitor and control the thickness of the layer of polycrystalline silicon as it is deposited. Typically this is done by complicated laser measurement system.
At least one attempt has been made to monitor the thickness of polycrystalline silicon deposition during its deposition using an infrared detector. See "In-Process Thickness Monitor for Polycrystalline Silicon Deposition", T. I. Kamins and C. J. Dell'Oca, Journal Electrochemical Society, January 1972, p. 112. This article describes the use of an infrared detector to observe the radiation emitted from an oxide-covered silicon wafer during the deposition of a polycrystalline silicon film on the oxide. However, the process did not provide a means to compensate for variations in radiation emissions which are due to variations in temperature or gas flow during processing.